"I think the audience will be shocked with what we do and what we reveal," he said. "The stuff that we answer... would normally take maybe a couple of seasons to answer.

"Like the big overlying questions that we set up in the first episode - those are going to be revealed come the finale, so it's pretty intense."

Gruffudd also insisted that fans will not feel disappointed by a lack of resolution in the episode.

"There are a couple of things that are unanswered but nothing in a sense that you feel betrayed," he claimed. "There are a few avenues that I'd like to explore more, but with what we have revealed, it might be difficult to go down that avenue."